Plant control systems have been rapidly migrating from proprietary, centralized architectures to open, decentralized fieldbus-based architectures such as FOUNDATION™ fieldbus from the Fieldbus Foundation (Austin, Tex.). FOUNDATION™ fieldbus specifies a lower speed fieldbus (H1) optimized for process control, and a High Speed Ethernet (HSE) fieldbus backbone for high performance control, subsystem integration, and management information systems integration. Exemplary H1 and HSE are described in the '872 patent, and the '697 application, respectively. Since FOUNDATION™ fieldbus is an open and interoperable, distributed control architecture, control devices from different vendors interoperate on the H1 or HSE fieldbus and share the control functions (e.g., control is distributed into the fieldbus devices). Distribution of control into the fieldbus devices reduces system installation cost because the need for centralized control computers and I/O subsystems are reduced or eliminated. Distribution of control into fieldbus devices reduces system operating and maintenance costs because function blocks in the devices provide more information about process measurements and device status. The demand for open and interoperable, distributed control fieldbus systems is driven by equipment suppliers and users. Suppliers want open and interoperable, distributed control fieldbus systems because it allows them to sell their products to more users, instead of only to users operating a specific proprietary system. Users want open and interoperable, distributed control fieldbus systems so that they can select the best control devices from multiple suppliers instead of only devices specifically designed for a proprietary system.
H1 provides the open and interoperable solution for field level control capability and integration, and HSE provides the open and interoperable solution for distributed control on a very high performance communication system typically called a fieldbus control “backbone” network. The HSE control backbone aggregates information from lower speed control devices, e.g., the H1 devices and other control devices, which is used in supervisory and advanced control applications. The HSE control backbone aggregates data from high-speed control devices, e.g., HSE devices and other subsystems, and provides access/change of H1 and HSE control information by control system computers.
Most plant automation application problems can be solved using standardized functions blocks as described in the '872 patent. The '872 function blocks have a fixed I/O configuration and a fixed control algorithm. However, certain applications have a need for function blocks where the number and type of inputs/outputs (I/O) and the function block algorithm are configurable by the end user. These user configurable blocks are needed for more complex discrete/hybrid/batch and PLC applications where the I/O and algorithms are application-specific.
Prior to the present invention, there was no way to generate interoperable end user configurable blocks needed for the discrete/hybrid/batch and PLC applications. End users were forced to develop custom control software and special I/O gateways, which were expensive and difficult to maintain.
What is needed is an open an interoperable fieldbus that can provide function blocks described in the '872 patent and '697 application as well as the end-user configurable blocks, thus eliminating the need for expensive and difficult to maintain custom control software and special I/O gateways.